Photographic products



United States Patent ()fi ice 3,226,844 Patented Nov. 30, 1965 3,220,844 PHOTOGRAPHIC PRODUCTS Robert C. Houck, deceased, late of Rochester, N.Y., by

Richard F. Houck, executor, Spencerport, N.Y., and

Donald A. Smith and Joseph S. Yudelson, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey N Drawing. Filed Sept. 19, 1961, Ser. No. 139,313 The portion of the term of the patent subsequent to Nov. 6, 1979, has been disciaimed and dedicated to the Public 11 Claims. (Cl. 96-85) This application is a continuation-in-part of our application Serial No. 786,227, filed January 12, 1959.

This invention relates to photographic emulsions in which water-soluble alkyl acrylate-acrylic acid polymer salts are used in substantial proportion as the vehicle for the silver halide therein or as a layer in a photographic paper between the paper base and the photographic emul- S1011.

Conventionally, photographic emulsions are made up of silver halide suspended in an aqueous solution of gelatin having therein various addenda, such as sensitizers, antifoggants, residual peptizer, and the like. These emulsions are useful for many purposes, but oftentimes certain properties exhibited thereby leave something to be desired. For instance, sometimes gelatin has a detrimental eifect on the stability of emulsions coated on low amplitude supports like Terylene or polycarbonate. Aqueous gelatin photographic emulsions when coated on unsized or waterleaf papers have a tendency to penetrate into the paper rather than remaining as a surface coat. In many cases supplemental materials have been suggested for addition to gelatin, but the resulting compositions when dried are often resistant to redispersion in water.

One object of our invention is to provide photographic emulsions having good dimensional stability and flexi bility characteristics when coated out upon various photographic supports. Another object of our invention is to provide silver halide emulsions which when dried are not resistant to redispersion in aqueous baths when use for coating upon a support is desired. A further object of our invention is to make possible the preparation of photosensitive papers using ordinary grade paper base whereby the photosensitive layer is retained on the surface of the paper. Other objects of our invention will appear herein.

We have found that the water soluble salts of certain copolymers of alkyl acrylates and acrylic acid in certain admixtures with gelatin not only provide a suitable vehicle for light-sensitive silver halide grains, but when so used provide an emulsion layer having a dimensional stability of the order of that of most of the stable film base materials. We have also found that the photographic emulsion layer resulting from such a composition when applied to polymeric type film base will produce a composite film product which will not tend to separate from the base in use. We have found that emulsions in accordance with the invention when placed on a dimensionally stable film base do not seriously derogate from the dimensional stability properties of the film base even when subjected to humid conditions. We have found that when the water-soluble salt of alkyl acrylate-acrylic acid copolymer is present in a gelatin-silver halide photographic emulsion used in applying as a coat onto paper or is used as a layer between the paper and the emulsion, the emulsion does not penetrate into the paper but remains on its surface, even though the paper base is an otherwise readily penetrable paper.

The copolymers for use in our invention are prepared by copolymerizing a mixture of an alkyl acrylate and acrylic acid. The alkyl acrylates of interest are those from methyl up to and including decyl. The materials found useful are the water-soluble ammonium or alkali metal salts of polymers made up of 50-90 mol percent alkyl acrylate and 50l0 mol percent acrylic acid. The polymer salt is 20-100 percent of the gelatin-resin vehicle employed in aqueous solution as the carrier for the silver halide. When acrylates of the alkyls from hexyl to decyl are used better water solubility is obtained if the proportion of acrylic acid in making up the polymer is at least about 30 percent.

The copolymer can be prepared by a number of different polymerization techniques. For instance, it may be prepared by a solution or dope polymerization method in the presence of a suitable catalyst. .After the polymerization has proceeded for the desired time, the reaction product may be precipitated by pouring the reaction mass into water, washing the precipitate and redissolving in water containing ammonium hydroxide. The copolymer may be prepared by emulsion polymerization or the like using an amount of acrylic acid within the range specified, following which the polymer is converted to the water soluble ammonium or alkali metal salt. The alkyl acrylate-acryl acid copolymers may be prepared by the hydrolysis of a polyalkyl acrylate such as polyethyl acrylate such as under alkaline conditions and stopping the reaction at the proper degree of conversion.

The following examples illustrate the preparation of photographic products employing our invention:

Example 1 A dimensionally stable polystyrene film base was coated with the following layers:

There was then applied a third subbing layer comprising a copolymer of ethyl acrylate and acrylic acid, :25 (not the salt). This polymer was dissolved in methanol to give a stock solution containing 15% by weight of the polymer. This stock solution was then employed in preparing the following composition:

Percent copolymer 1 Methyl Cellosolve 15 Water 15 Acetone 25 Methanol 44 and the polystyrene base was then subbed with this solution by a bead coating method. There was then applied to the resulting polystyrene film base a photographic emulsion having the following composition:

4.25 parts of ammonium salt of the copolymer of ethyl acrylate and acrylic acid in which acrylic acid comprises 25 mol percent 0.75 part of gelatin 5 parts of silver halide parts of water Coatings were also made using this emulsion with 4% (based on the weight of the polymer) of bis(2,3-epoxypropoxyethyl)ether therein. The emulsion coatings were aged for two days at 50% RH. and 75 F. temperature. The adhesion of the emulsion coatings to the film base was excellent, both after coating and after processing in developer, fixer and water wash.

Example 2 To 1870 g. of a washed sulfur-sensitized fine-grain silver bromoiodide emulsion containing 0.98 mol of silver halide and 49 g. of gelatin per mol of silver halide, was added 4.21 kg. of a 6.84% solution of the ammonium salt of a copolymer of ethyl acrylate and acrylic acid (the acrylic acid comprising 20% by Weight of the polymer) and 8.84 g. of bis(2,3-epoxypropoxyethyl)ether hardener. This emulsion was coated on polystyrene film base and dried with warm air. The film was aged months at 70 F. and 50% RH. and was then given a second exposure through a step Wedge to light of 3000 K. color temperature, developed 8 minutes in Kodak Developer DK-SO, fixed 10 minutes in Kodak Fixer F-24 and washed with water. The following results were obtained:

1 Log of the exposure at a density of 0.3 over gross fog.

An emulsion similar to the above was prepared except that 4.21 kg. of a 6.84% solution of gelatin and 1.75 g. of formaldehyde were substituted respectively for the acrylic acid-ethyl acrylate copolymer salt and bis(2,3- epoxypropoxyethyl)ether. The two emulsions were each coated on film bases made from polystyrene, poly(ethylhyde. The emulsion and the solution were coated simultaneously onto a support of ordinary grade paper by the method described in US Patent 2,761,791 of T. A. Russell, the solution being next to the support. The silver halide emulsion was at a coverage of approximately 0.5 lb. of emulsion per 100 sq. ft. and the solution at a coverage of 1.5 lbs. per 100 sq. ft. A photosensitive paper was obtained in which the photosensitive layer is retained only on the surface of the paper.

Example 5 A series of coatings of silver halide gelatin emulsions containing ethyl acrylate-acrylic acid copolymer salt in various proportions were coated out onto a partially acetylated paper support of the type described in Richter and Herdle application Serial No. 755,418. The coatings were applied at a rate of 0.4 g. per square foot of paper. The compositions of the vehicle in the respective emulsion mixtures were as follows: 100% gelatin, 80% gelatin-% of ammonium salt of ethyl acrylate-acrylic acid, 60% gelatin-40% of ammonium salt of ethyl acrylate-acrylic acid copolymer, 40% gelatin-60% of the polymer salt, and 20% gelatin80% of the polymer salt. Samples of these coatings were processed with Kodak Dektol Developer 1:2 (60 seconds at 68 F.); 1% acetic acid stop bath(15 seconds); Kodak F-5 fixing bath (5 minutes); 10 minutes Washing in running Water and were dried. The dried samples were run through a Paragon Revolute Rocket printer at 12 ft. per minute. The printer temene terephthalate), and cellulose triacetate. The followperature was 210 F. and room humidity was 50% RH. ing dimensional properties were observed: The samples were udged for curl after the first, fifth and Humidity mm. Hu- Amplitude midity Curl Emulsion Vehicle Film Support (2070% Amplitude RH.) Raw (IO-70% (Percent) RH.) Raw Ethyl acrylate-acrylic' acid copol- Polystyrne .009 .01

ymer salt and gelatin. Gelatin do 065 18 Ethyl acrylate-acrylic acid copol- Poly(ethylene- .026 .00

ymer salt and gelatin. terephthalate). Gelatin d0 075 13 Ethyl acrylateacrylic acid copol Cellulose Triacetate .170 .00

ymer salt and gelatin. Gelatin rln 228 25 Example 3 tenth passes of the samples through the printer. At every To a silver bromoiodide-gelatin emulsion weighing 3.75 kg. and containing 203 g. of gelatin per mol of silver halide (92% water content) was added 5 kg. of an 8.74% solution in Water of ammonium salt of ethyl acrylateacrylic acid polymer (80:20), 1.7 liters of distilled water, 37 mg. of a 10% aqueous solution of sodium sulfite, 18 mg. of a 15% aqueous solution of formaldehyde and 215 ml. of a 5% solution of butane diol bisglycidyl ether in methanol. This photographic emulsion was coated at the rate of 1600 sq. ft. per mol of silver halide onto an unsized low-cost paper support (Clear Spring Register Bond, a 10 lb. commercial typewriter paper) and dried. A sample of this paper was exposed to a microfilm negative at 22 enlargement. The exposed paper was developed in Kodak Dektol 1:1 for 60 seconds, and was fixed and dried. A dimensionally stable photographic paper projection print of good characteristics was obtained.

Example 4 A silver bromoiodide-gelatin photographic emulsion as described in the preceding example was employed. 18.5 ml. of p-tert. octylphenoxyethoxyethyl sodium sulfate in water solution per liter of photographic emulsion was added as coating aid. A solution was prepared containing 16 kg. of 8.74% of the ammonium salt of ethyl acrylate-acrylic acid copolymer (80:20), 160 ml. of 10% sodium sulfite, 223 g. of colloidal silica (Syloid) in 3 liters of distilled water, 633 ml. of butane diol bis-glycidyl ether and 300 ml. of a 15 aqueous solution of formaldestage the sample in which the gelatin vehicle only was used showed the severest curl, becoming progressively less severe asthe proportion of ammonium salt of ethyl acrylate-acrylic acid polymer increases. The samples having the higher proportions of polymer salt lay fiat after emerging from the printer.

Several advantages are obtained in preparing photosensitized paper from emulsions containing as a considerable proportion of the vehicle a water-soluble salt of alkyl acrylate-acrylic acid copolymer or when that salt is applied to the paper immediately prior to the application of the photosensitive emulsion thereto:

(1) When emulsions containing the polymer salt are coated on unsized paper support the aqueous emulsion tends to remain on top of the paper stock, with little tendency to strike through the base and thereby cause cockle of the paper. This is more pronounced with amounts of the polymer salt at least equal to that of the gelatin.

(2) Incorporating the polymer salt in silver halide gelatin emulsions in accordance with the invention decreases the tendency of layers thereof to curl while wet in the coating machine or after drying. This decrease in tendency to curl is particularly pronounced when the proportion of polymer salt is at least equal to that of the gelatin.

(3) The addtion of polymer salt gives high coatability because it is possible to coat lower amounts of emulsion pe unit area and thereby give thinner coatings than is possible when gelatin only is used as the vehicle, which property is particularly beneficial at high coating speeds.

(4) Silver halide gelatin emulsions containing polymer salt exhibit a much greater hypo elimination rate than emulsions in which only gelatin is employed as the vehicle.

(5) The presence of alkyl acrylate-acrylic acid copolymer salt results in a decrease of tackiness or stickiness.

(6) Silver halide emulsions containing the salt of alkyl acrylate-acrylic acid polymer when coated on light-weight papers have considerably more physical strength than similar coatings in which only gelatin is used.

(7) Using a layer of water-soluble salt of alkyl accrylate-acrylic acid copolymer between the emulsion layer and paper support is particularly useful in the case of papers intended for surface application processing in which very small amounts of solution are applied to the surface.

All of the examples given make use of ethyl acrylate as the acrylate component of the polymer, which is preferred. However, other alkyl acrylates may be employed such as those of alkyls from 1 to 10 carbon atoms. In some cases, it may be desirable in employing mixtures of gelatin and acrylate-acrylic acid copolymer salts as vehicles of silver halide emulsions to also include a hardener, particularly of the epoxy type, in the composition. For instance, the use of up to 10%, based on the Weight of the polymer of an epoxy hardener such as bis(2,3-epoxypropoxyethyl)ether is sometimes desirable in the emulsion compositions.

We claim:

1. A silver halide photographic emulsion in which -100% of the vehicle for the silver halide, dry weight, is a water-soluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 5090 mol percent of alkyl acrylate and 50-10 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

2. A silver halide photographic emulsion in which 20100% of the vehicle for the silver halide, dry weight, is a water-soluble salt of ethyl acrylate-acrylic acid copolymer composed of 50-90 mol percent of ethyl acrylate and 5010 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

3. A silver halide photographic emulsion in which 20-100% of the vehicle for the silver halide, dry weight, is an ammonium salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent alkyl acrylate and 50-10 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

4. A silver halide photographic emulsion in which approximately 85% of the vehicle for the silver halide is an ammonium salt of ethyl acrylate-acrylic acid copolymer essentially consisting of approximately 75 mol percent of ethyl acrylate and mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

5. A photographic element comprising a polystyrene film support and a layer of a silver halide photographic emulsion thereon, in which emulsion 20-100% of the vehicle for the silver halide is a water-soluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent of alkyl acrylate and 50-10 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

6. A photographic element comprising a polyterephthalate film support and a layer of a silver halide photographic emulsion thereon, in which emulsion 20- of the vehicle for the silver halide is a watersoluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent of alkyl acrylate and 5010 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

7. A photographic element comprising a cellulose triacetate base and a layer of a silver halide photographic emulsion thereon, in which emulsion 20100% of the vehicle for the silver halide is a water-soluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent of alkyl acrylate and 50- 10 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

8. A photographic element comprising a paper base and a layer of a silver halide photographic emulsion thereon, in which emulsion 20-100% of the vehicle for the silver halide is a water-soluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent of alkyl acrylate and 5010 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin.

9. A photographic element composed of a paper support containing thereon a photographic silver halide emulsion layer and between the emulsion layer and the paper support a layer of a water-soluble salt of an alkyl acrylate-acrylic acid copolymer.

10. A silver halide photographic emulsion in which 20100% of the vehicle for the silver halide, dry weight, is a water-soluble salt of an alkyl acrylate-acrylic acid copolymer essentially consisting of 50-90 mol percent of alkyl acrylate and 50-10 mol percent of acrylic acid, substantially the remainder of the vehicle being gelatin, which emulsion contains up to 10%, based on the weight of the polymer, of an epoxy type hardener.

11. A photographic element comprising a paper base and a layer of a silver halide photographic emulsion thereon, in which emulsion 20100% of the vehicle for the silver halide is a water-soluble salt of an alkyl acrylate acid copolymer, substantially the remainder of the vehicle being gelatin, which emulsion contains up to 10%, based on the weight of the polymer, of an epoxy type hardener.

References Cited by the Examiner UNITED STATES PATENTS 1,981,102 11/1934 Hagedorn et al. 96-114 2,565,418 8/1951 Yackel 96--114 2,835,582 5/1958 Fowler 96-114 2,956,884 10/1960 Caldwell 96--114 3,062,674 11/1962 Houck et al. 961 14 NORMAN G. TORCHIN, Primary Examiner.

HAROLD N. BURSTEIN, Examiner. 

9. A PHOTOGRAPHIC ELEMENT COMPOSED OF A PAPER SUPPORT CONTAINING THEREON A PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER AND BETWEEN THE EMULSION LAYER AND THE PAPER SUPPORT A LAYER OF A WATER-SOLUBLE SALT OF AN ALKYL ACRYLATE-ACRYLIC ACID COPOLYMER. 